1. Field of the Invention
The present invention relates to a toll collection system for a toll road which can perform toll collection transactions with a vehicle on the toll road without stopping the vehicle at a toll gate, and further relates to an in-vehicle unit for the toll collection system.
2. Description of Related Art
A toll collection system of this kind for a toll road is disclosed, for example, in Japanese Patent Publication Laid-Open No. Sho 63-127392. In this system, first and second on-road units are arranged sequentially in the advancing direction on the lanes of an entrance toll gate of a toll road, and a ticket issuer for issuing a ticket according to the toll is disposed behind the second on-road unit. In a passing vehicle, moreover, there is carried an in-vehicle unit which can communicate with those on-road units so that the toll is automatically collected by communicating with the passing vehicle.
In this construction, when a vehicle advances to the entrance toll gate, the first on-road unit communicates at first with the in-vehicle unit, as carried in the vehicle, to recognize the ID card of the vehicle. At this entrance toll gate, the clerk discriminates the vehicle class indicating the classification for calculating the toll. In the case of success in the communication by the first on-road unit, moreover, the second on-road unit then transmits the data of the entrance toll gate and the vehicle class data to the in-vehicle unit and causes that data to be written in the in-vehicle unit. Upon the failure of the communication by the first on-road unit, on the other hand, the entrance toll gate data is not recorded in the in-vehicle unit so that a ticket for the vehicle is issued by the ticket issuer so that the driver can receive it.
By providing this construction, when the vehicle carries the in-vehicle unit and operates in a normal state, it can pass without stopping at the entrance toll gate thereby reducing the complexity of the toll collection and reducing the traffic congestion at the entrance toll gate.
In the aforementioned construction, however, the vehicle class data are discriminated by manual means so that the discrimination takes considerable time. When the running speed of the coming vehicle exceeds a predetermined value, it may pass through before the completion of the communication of the vehicle class data and the entrance toll gate data by the second on-road unit. In other words, the running speed on the toll gate lanes has to be limited to a predetermined value or less so that the vehicle class data and the entrance toll gate data may be written without fail.
As the system for deciding the vehicle class data automatically, on the other hand, there is a vehicle class discriminator which is disposed at an entrance toll gate of an existing toll road. This discriminator is disposed at a position of about 20 meters on the entry side of the ticket issuer. Before the vehicle to pass passes through the vehicle class discriminator to the position of the ticket issuer and stops, the ticket issuer issues a ticket corresponding to the vehicle class as discriminated by the vehicle class discriminator.
Incidentally, this automatic vehicle class discriminator is arranged assuming that the vehicle stops at the position of the ticket issuer, as described above, so that the distance to the ticket issuer is set short. When the aforementioned toll collection system is to be applied, it is also impossible to retain the time period for the writing operation of the second on-road unit reliably.